1. Field of Invention
The present invention relates generally to holding fixtures to enable machining operations to be accurately performed on a work piece. Specifically, the invention enables machining operations to be accurately and repeatedly performed on different types of successive work pieces while requiring a minimum of set-up time.
2. Description of the Prior Art
In many instances, the shapes of structural assemblies for the fuselage and airfoils of modern aircraft are of highly irregular and complicated shapes. This frequently results from attempts to achieve optimum aerodynamic efficiency. At the same time, it often occurs that by reason of a relatively small production run of the item, there is an insufficient quantity of the item being produced to warrant the hard tooling which would otherwise be necessary for machining operations. It will be appreciated that the time and expense involved in providing hard tooling can be very great indeed.
Therefore, previously, it was the custom when small production runs were called for, to perform manually such machining operations as sawing, milling, grinding, and drilling. Unfortunately such operations were necessarily performed with substantial loss of time, and in some instances, accuracy and repeatability. Often times, the work piece would be manually and visually placed on the work surface of the machine tool, then clamped into position until all operations have been completed. The clamp itself, in order to securely hold the work piece, sometimes undesirably deformed the work piece in an effort to prevent movement during the machining operation. Also, the clamp was subject to inaccuracies and with wear after a time might no longer rigidly hold the work piece. It was with recognition of these and other drawbacks of the prior art that the present invention was conceived and has now been reduced to practice.